BOSTON -- J.A. Happ has already won 20 games in his Cy Young-worthy season. But Saturday night, the left-hander makes what may well be the biggest start of his life.

Happ, 20-4 with a 3.20 ERA, faces the Boston Red Sox and young lefty Eduardo Rodriguez in the second game of the last-weekend series.

The Blue Jays came to Boston for the David Ortiz weekend tied with the Baltimore Orioles for the two American League wild card spots. They lost Friday night, falling one game behind Baltimore and shriking their lead over Detroit to one-half game and Seattle to a full game.

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The Red Sox remain one-half game ahead of the Cleveland Indians for home-field advantage in their upcoming American League Division Series.

"We kind of anticipated this might be the way that it shakes out," manager John Farrell said of meeting the Indians and former Red Sox manager Terry Francona, his old friend and boss. "Obviously a very good team. We'll have time to review them more in depth as is typically the case when we get ready for the postseason, but we're loomking forward to these final two games here."

Happ, who has won 27 of his last 33 decisions dating back to late last season with the Pittsburgh Pirates, is 2-0 against the Red Sox this season, 5-3 with a 3.74 ERA in his career and 2-1 with a 4.34 at Fenway Park.

Happ is trying to become the first left-hander in Jays history to win 21 games. He allowed 164 hits in 188 2/3 innings this season.

In two starts against Boston this season, Happ, known for his unflappable demeanor and lack of emotion on the mound, has allowed three earned runs in 13 innings.

"Don't let him fool you," staffmate Marcus Stroman told the Toronto Star this week. "He's very emotional. He just doesn't show it on the field.

"There'll be times when he gets a big out and he'll come in (the dugout) and let out a big yell, or if he's frustrated he'll let a little fire out under the tunnel. But he's cool, calm and collected on the mound."

Red Sox hitters do not have very good numbers against Happ with Xander Bogaerts coming in at 1-for-15, Mookie Betts 2-for-14, David Ortiz 3-for-16 and Dustin Pedroia 6-for-26.

Rodriguez, coming off striking out 13 in 5 1/3 innings in his last start, has a 3.10 ERA in 13 starts since returning from the minors and is the likely Game 4 starter for the Red Sox in the ALDS. He has limited opposing hitters to a .171 batting average over his last eight starts.

"Eddie going down to Pawtucket, working on some things, the adjustments he made delivery-wise, coming back with three more defined pitches," Boston manager John Farrell said of Rodriguez, who got 13 of 16 outs against the Rays via the strikeout.

Rodriguez has lost twice in as many starts against Toronto this season (only two earned runs in six innings at Toronto on Sept. 10) and is 1-3 with a 6.85 ERA lifetime against the Jays.

The current Toronto roster has six home runs in 71 at-bats against Rodriguez, including one apiece by Jose Bautista and Edwin Encarnacion. But Josh Donaldson is 1-for-10 and Kevin Pillar 1-for-8 against him.